Electric bikes – the battery saga

It’s still ongoing, but much less of an issue. Sorting out battery issues is a slow process when it’s the charging/discharging side of things you have an issue with.

I replaced the faulty (possibly) cell with a new fully charged one, when the battery was fully charged, and everything was good. Next time I charged, the replaced cell only charged to about 3.4v, a little odd. Suspecting the BMS, I switched cells 1 and 2 around, and next time I charged, the same thing happened – cell 1 low, the original cell 1 which is now cell 2, up to 3.65v)! All the other cells are going a bit too high (3.8v) to compensate for the low cell.

So, I decided the BMS was faulty, and order a couple of Smart BMS from BMSBattery. The Smart BMS are programmable if you have the adapter, but they will program them from the factory for you. I had them program the cell overcharge value to 3.65v, to protect my valuable cells from an early death due to continuous overcharging. I also had them set the over-discharge cutoff voltage to 2.0v, which in hindsight is possibly a bit low, 2.2v is a better value for this. Hopefully, the controllers low voltage cutoff will stop this one ever being used.

Apparently BMS stands for “Blue My Sky” as well as Battery Management System – you have to love the Chinese English Teachers!

In the meantime, while waiting for the BMS to arrive I decided to do a monitored charge of the battery taking the BMS out of the system completely. Strangely, cell 1 stayed low again, and for the last few charges has stayed down at 3.36v. This has the annoying consequence of the BMS balancing the battery down to the same voltage on each cell, reducing the total voltage, and hence the range by a small but noticeable amount. So its possible that this cell is a little weak too.

As I write I am charging the battery again, and have also used the single cell charger to charge both of the two spare cells, one new one, and the old cell that manage to totally discharge somehow. Funnily enough, this old cell is charging quite nicely up to 3.65v, and is retaining its charge quite well when not in use. While I am not likely to put it back into a battery any time soon, I will hang on to it, keep it charged, and maybe find a use for it somewhere. Back to the current battery – when it is charged, I intend to swap out the low voltage cell 1 and replace with a the fully charged new cell, reconnect the BMS and see what the BMS and 40km of riding does to it. I will post more when I recharge it, and also when the new BMS arrives.

In other news – in 40km the e-bike will have done 2000 km, the newly rebuilt rear wheel is wonderful, smooth, braking well, running true and with a new tyre feels much more secure. We are having a beautiful New Zealand Summer, hot clear, little rain and little wind most of the time, and it is really good to have the bike back on the road again and getting some kms on it. Lynn’s bike is similarly good, and is being used daily for commuting. I don’t think the Honda has been out of the garage for 5 or 6 days now!

The roads are full of bikes, I see dozens go past the front of the shop everyday. Lynn even showed one rider the way north out of Porirua a couple of days ago, a young man called Tom from Warrington in Cheshire UK, here on a working holiday. I think he was quite impressed with the electric bike and the speed Lynn kept up on the hills!

We are seeing more and more electric bikes, quite a few Ezee bikes around, I saw a Bosch mid drive system a few weeks ago, and there is an EvLab conversion (or at least has an Evlab battery base) dashing around the Papakowhai area. Four guys were seen cycling around the inlet, one of the guys who was substantially overweight was on an e-bike, and looked comfortable keeping up with his mates on their normal bikes. It makes me feel good every time I see one – the future is e-bikes, whether petrol heads or “vehicular cyclists” like it or not. In fact, electric bikes open up the concept of vehicular cycling to all riders, whether road warriors or not. Older or less fit riders can still be confident road users with a little assistance.

I bought Lynn and myself a “Rearviz” mirror each for xmas. These are really cool rear view mirrors, which we wear on our arms, not fit to the bike. They might look a bit dorky, but slipping in and out of the traffic is much easier with a good view of what is behind you!

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